All documents referred to herein, or the indicated portions, are hereby incorporated by reference herein including U.S. Provisional Application Ser. No. 61/223,005, filed Jul. 3, 2009. No document, however, is admitted to be prior art to the claimed subject matter.
Approximately 60,000 cases of disseminated candidiasis occur per year in the United States [1], resulting in billions of dollars of health care expenditures. Given the 40% mortality rate of such infections, there is a need to identify new prophylactic or therapeutic targets for intervention.
The primary host defense mechanism against disseminated candidiasis is phagocytic killing of the organism [2, 3]. Only phagocytic cells are capable of directly killing Candida in vitro [4]. Additionally, within thirty-minutes of intravenous inoculation of Candida in mice, rabbits, dogs, or humans, yeasts are retained within the reticuloendothelial system, especially in the liver. The liver, rich in Kupffer macrophages, is capable of clearing 99.9% of yeast in the portal system during a single pass [5], underscoring the effectiveness of phagocytic defense mechanisms against the fungus. Hence, resistance of C. albicans to phagocyte killing is an important virulence function of the organism.
Cell surface glycosyl phosphatidylinositol (GPI)-anchored proteins are at the critical interface between pathogen and host, making these proteins likely participants in host-pathogen interactions [6].
The identification of effectors in the regulatory pathways of the organism that contribute to virulence offers the opportunity for therapeutic intervention with methods or compositions that are superior to existing antifungal agents. The identification of cell surface proteins or hyphal proteins that affect a regulatory pathway involved in virulence is particularly promising because characterization of the protein enables immunotherapeutic techniques that are likely superior to or synergistic with existing antifungal agents when fighting a candidal infection.
The virulence of C. albicans is regulated by several putative virulence factors of which adherence to host constituents and the ability to transform from yeast-to-hyphae are among the most critical in determining pathogenicity. While potent antifungal agents exist that are microbicidal for Candida, the attributable mortality of candidemia is approximately 38%, even with treatment with potent anti-fungal agents such as amphotericin B. Also, existing agents such as amphotericin B tend to exhibit undesirable toxicity. Although additional antifungals may be developed that are less toxic than amphotericin B, it is unlikely that agents will be developed that are more potent. Therefore, either passive or active immunotherapy to treat or prevent disseminated candidiasis is a promising alternative to standard antifungal therapy.
Thus, there exists a need for effective immunogens that will provide host immune protection and passive immunoprotection against Candida and other immunogenically related pathogens. The present invention satisfies this need and provides related advantages as well.